Abstract Background The incidence of end-stage heart failure necessitating advanced cardiac therapy continues to increase in the United states. Implantable left ventricular assist devices (LVADs) represent an important modality that is utilized both as a bridge to heart transplant or as destination therapy. LVAD-associated infections, ranging from driveline exit site or pocket infections to endovascular infections, are a major complication with high mortality. Antibiotic prophylaxis at time of LVAD implantation is therefore an important strategy to mitigate infections. However, a clear surgical infection prophylaxis regimen and associated outcomes have not been reported. Methods We performed a single center, retrospective cohort study evaluating the impact of antimicrobial prophylaxis on risk of infection in patients who underwent LVAD implantation between February 2007 and June 2019 at Mayo Clinic. LVAD-specific and related infections were defined according to the International Society of Heart Lung Transplantation criteria. Single drug prophylaxis (SDP) included cefazolin only, vancomycin only, or cefazolin and vancomycin; multidrug (MDP) regimen includes either of the SDP regimens plus another antibiotic. We compared incidence of infection within 90-day and within one-year of implantation, as well as risk of C. difficile infections between the SDP and MDP cohorts. Results We reviewed 403 patients who received LVAD implantation (Table 1), 402 of had information on surgical prophylaxis. 307 (76%) patients received SDP and 95 patients (24%) received MDP. 14 patients developed an infection within 1 year of implantation (Table 2). There was no difference in the incidence of infections between SDP and MDP arms both at 90 days and 1-year post-implantation (p=0.11). The median time of infection since LVAD implantation was similar between SDP and MDP (p=0.37) arms. Incidence of C. difficile infection was not different between groups (p=0.10) (Table 3). Conclusion There was no significant difference in incidence or time to first infection, within 90-day and 1-year of implantation, between single- and multidrug antibiotic surgical prophylaxis regimens administered at the time of LVAD implantation. Future prospective trials are needed to develop a clear LVAD antibiotic prophylaxis protocol. Disclosures John C. O'Horo, Sr., MD, MPH, Bates college: Advisor/Consultant|MITRE corporation: Grant/Research Support|nferenec, Inc: Grant/Research Support.